NDTnet 1998 Aug, Vol.3 No.8

Abstract

Mechanised and automated ultrasonic pipeline girth weld examination systems (AUE), including the use of time-of-flight diffraction (TOFD), are now so far developed, that they seem to be able to serve as a reliable alternative to radiography during pipeline construction and such equipment has also been taken into use for some land pipelines. During offshore pipe laying, where time is very limited for doing non-destructive examination (NDE) between welding and lowering of the pipe onto the seabed, AUK have so far only found limited application. The available systems do, however, also for this type of application bear potentials, as they will shorten the time required for NDE, and thus contribute to shorten the fabrication time, making the pipe laying more cost-effective. In addition, they have the potential of revealing the more severe defect types like lack of fusion, which are not always readily detected by radiography, and, through the better quality control work, reduce repair rates.

One of the questions raised, when evaluating AUK to replace radiography, is the question of the reliability, and how the results should be interpreted, i.e. how should acceptance criteria be formulated. This topic has been addressed by users of AUK, and is now also addressed on a general basis in an international project under the auspices of the International Pipe Line & Offshore Contractors Association (IPLOCA) with support from pipeline authorities, operators, contractors and NDE service companies.

The objectives of the project are to develop ultrasonic acceptance criteria equivalent to the presently used radiographic ones, and to demonstrate their adequacy. The project therefore includes an experimental reliability data acquisition and verification programme, which is outlined. Results to be achieved, and evaluations to be done, are exemplified using available non-destructive examination reliability results from other investigations. At a later stage also fitness-for-purpose acceptance criteria will be addressed.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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